Magnetic ore separator and classifier



Jan. 24, 1939. M R|$T 2,144,796

MAGNETIC ORE SEPARATOR AND CLASSIFIER Filed Nov. 3, 1934 4 Sheets-Sheet1 izy INVENTOR 00/1/1410 /7 C/P/ST ATTORNEY Jan. 24, 1939. D M. CRISTMAGNETIC ORE SEPARA'IOR AND CLASSTFIER Filed Nov. 3, 1934 4 Sheets-Sheet2 I IT'IIII WM m 0 W W m Jan. 24, 1939.

D. M. CRIST 2,144,796

MAGNETIC ORE SEPARA'I'OR AND CLASSIFIER Filed Nov. 3, 1934 4Sheets-Sheet 3 Hil HIWE HI HIHIHI mun numlll n m Hm I I! ll "Will H IIN, 02

INVENTOR DOA/A40 M CAD/S7- ATTORNEY Jan. 24, 1939. o M. CRIST MAGNETICORE SEPARATOR AND CLASSIFIER Filed Nov. 3, 1934 4 Sheets-Sheet 4 nnnnnn:

nnnnnn INVENTOR. Doxvauo /7. 6/2/67- Wm v A TTORNEYS.

Patented Jim. 24, 1939 2,144,796

UNITEDSTATES PATENT OFFICE 1 MAGNETIC ORE SEPABATOR' AND CLAS SIFIERDonald M. Grist, San Francisco, Calif., assignor to Titanium Steel AlloyCompany, a corporation of Delaware Application November 3, 1934, SerialNo. 751,273

7 Claims. (Cl. 209-423) This invention relates primarily to magneticconstituents are brought to a stop before reachore separators and hasfor an object to proing each unit, and hence are caused to pass videmechanism whereby several ore constituents each unit under the samegravitational force, of difierent magnetic susceptibilities may besepthere being no impairment of the effectiveness arated and classified.of the latter units because of any previously 2.0- 5

The invention also has to do with interrupter quired velocity of the oreparticles. The sepamechanism for intermittently interrupting the rationefiected depends solely upon the magnetic supplying of current to theelectromagnets emcharacteristics of the ore particles and is indeployedin the apparatus while avoiding objecpendent of variations in the massof the par- 10 tionable back discharge of high voltage. Such tlcles. 10

means serves to prevent accumulation of ore In effecting the separationof the ore constituagainst the faces of the electromagnetic units. cutsof low magnetic susceptibility, it is neces- The interrupter mechanismof the present insary to employ powerful electromagnets and vention isespecially designed for this use but these in turn require that manyampere turns itis capable of use in other apparatus. of current besupplied to them. These electro- 15 In accordance with a preferredembodiment of magnets tend to hold the separated particles theinvention, the electromagnetic units may all and completely to overcomethe effect of gravity be arranged in stepped relation in a continuous sothat there is a tendency for the material to upstanding series. Theseunits are associated accumulate and choke the apparatus or impair ingroups, the units of each group being all conthe intended operation.Provision is accordingly 20 nected to discharge ore to a common pointand made for temporarily interrupting the supply of all having the samemagnetic densities and current to the electromagnets at intervals. Ifcharacteristics. The units of the first group dethe high density currentsupply were instantasirably comprise relatively weak magnetsadaptneously cut oil, there would be an inductive dised only to attractand separate the ore concharge transmitted through the system, origi- 25stituent of highest'magnetic susceptibility. The nating at theelectromagnets, which discharge units of the second group employ morepowerwould be of much higher voltage than the enful magnets, capable ofremoving or recovering ergy normally supplied from the generator or theore constituent of next highest magnetic sus- Other source. Such backdischarge has been ceptibility but incapable of acting upon the lessfound to be very destructive or insulation, dam- 30 magnetic particles.There are as many groups aging to the generator, and almost uncontrolasthere are ore constituents to be separated and lable.

each group employs more powerful magnets than To overcome thesedifficulties interrupter the next preceding group. mechanism isintermittently operated to grad- It is a characteristic of the oreseparator oi ually interpose an increasing resistance in each 35 thepresent invention that the magnetic influence electromagnet circuit andfinally to short-circuit is applied while the ore particles (the orebeing the electromagnet. The inductive discharge in a finely dividedstate) are falling freely under originating at the electromagnet isconfined to the influence of gravity and are not in contact a loopcircuit including the electromagnet and with one another. In passing anyunit, the ore cannot reach the generator to affect it detri- 40constituents not responsive to the magnetic mentally. strength of thatunit fall directly by gravity Other-objects and advantages willhereinafter into a hopper and pass thence to the succeeding appear. Iunit. The particles of the ore which are sus- In the drawings formingpart of this specifiepticle to the magnetic strength of the first unitcation and showing certain preferred 'embodi- 45 are retarded in theirfall and diverted by the ments of the invention, magnetic pull, beingcaused to drop into a dif- Figure 1 is a fragmentary view in elevationferent receiver and to be transferred out of and partly diagrammaticillustrating an appatHe system to a point of accumulation. The unitsratus embodying the invention;

- are arr n in r p n order t make re Figure 2 is a diagrammatic viewillustrating so that the separation will be substantially comthe circuitarrangement of a single electroplete and perfect, the several units of asingle' magnet; group being all designed for the separation of Figure 3is a fragmentary view in elevation the same ore constituent.illustrating substantially a pair of successive It is a feature of theinvention that the ore units;

Figure 4 is a detail view in sectional elevation illustrating a portionof the interrupter mechamsm;

Figure 5 is a view in front elevation of the mechanism illustrated inFigure 3;

Figure 6 is a transverse, vertical, sectional view illustrating certainfeatures of one of the electromagnetic units;

Figure 7 is a horizontal sectional View taken on the line 7-1 of Figure6 looking in the direction of the arrows;

Figure 8 is a horizontal sectional view taken on the line 8-8 of Figure6 looking in the direction of the arrows;

Figure 9 is a plan view partly broken away illustrating another form of,electromagnetic unit as employed in the last series of units;

Figure 10 is a fragmentary view in side elevation, partly broken away,showing features of the electromagnetic unit of Figure 9;

Figure 11 is a plan view illustrating a modified form of interruptermechanism adapted to be used in place of that of Figure 4;

Figure 12 is a vertical, sectional view of the interrupter mechanism ofFigure 11, and

Figure 13 is a fragmentary sectional elevation on a larger scale thanFigure 3, but showing substantially the same part of the apparatus asFigure 3.

The illustrative magnetic separator comprises a supply hopper I fromwhich the ore in finely divided form is discharged into the separatingapparatus in a thin blanket. The ore passes successively through theunits 2, 3, 4 and 5 of the first series. All of these units areidentical and are designed for the separation of a single oreconstituent of highest magnetic susceptibility. The magnets of theseunits are relatively weak magnets incapable of influencing any of theother ore constituents. The units of this series are all alike and areas illustrated in Figure 3.

The ore constituent of highest magnetic susceptibility is thoroughlyseparated out by the units 2, 3, 4 and 5 and the remaining ore thenpasses successively through the units 6, I, 8 and 9. These units employelectromagnets which are more powerful than the magnets of the firstseries and are designed to separate out the ore constituent of nexthighest magnetic susceptibility.

Similarly, the ore which remains unseparated ore constituent of stilllower magnetic susceptibility, these last mentioned units including themost powerful electromagnets of all.

The units 2, 3, 4 and 5 all discharge the separated ore into a commonconduit l8; the units 6, I, 8 and 9 all discharge the ore separated bythem into a common conduit IS; the units II), II, l2 and I3 alldischarge the ore separated by them into a common conduit 20; and theunits l4, I5, I6 and I! all discharge the ore separated by them into acommon conduit 2|.

The units of the first group may employ magnets which are simple,permanent magnets since very little magnetic force is required to exertthe necessary influence upon the ore constituent of highest magneticsusceptibility. For the purpose of rendering the apparatus adaptable fordifferent ore bodies, however, it may be preferable to employ in theseunits electromagnets of the same type employed in the second and thirdgroup as illustrated in Figures 3 and 6.

Mechanically, the units are all duplicates and the operation will bereadily understood from the disclosure of Figure 3. This figure shows apair of intermediate units which may be assumed to be the units 7 and 8.The ore material, which passes the unit 6 without separation, iscollected in a hopper 22. Each hopper 22 is mounted to discharge oreonto the top of a non-magnetic plate 25 (preferably of brass) which isfastened to the pole plates 26 and 27 of the electromagnetic unit, thelatter being in turn supported on brackets 28, pivoted at 29 to theframe 30.

The plate 25 extends across the front of and above the magnet, beingrearwardly offset at its upper end 3 I. The hopper 22 is supported onthis offset portion 3| of the plate so that the discharge spout 32 ofthe hopper which extends rearwardly and downwardly will discharge oreonto the plate 25 at a point above that portion of the plate whichextends over the front of the magnet. The discharge spout 32 of thehopper is inclined down very slightly, being almost horizontal, so thatany downward velocity of the ore particles is completely checked and theore is -caused to reverse its direction of flow before being deliveredonto the offset portion 3| of the plate 25. The plate 25 does not extendvertically downward but is inclined slightly so that it overhangs achute 33 and the mouth of a collecting chute 34. The ore which dropsdownward across the face of the plate 25 if permitted to fall freely andwithout deflection by the magnetic force would all fall onto the upperend of the guide chute 33 andbe delivered thereby to the hopper 22 ofthe next unit. The particles of ore which are susceptible to theinfluence of the magnetic unit under consideration are slowed up,however, and drawn rearward toward or into contact with the plate 25 andclear of the upper end of the chute 33. This portion of the ore istherefore separated and caused to fall into the collecting chute 34. Inthis connection, it will be noted that the plate 25 extends downwardlyand rearwardly and that its lower end is extended rearward and into thechute 34.

The chute 33 comprises a deflecting plate 35 which has its upper edgedisposed close to the plate I I at a point above and to the rear of theforward edge of the upper end of the chute 34, while the plate extendsdownwardly and forwardly so that its lower end extends into the hopper22 for the'next unit. The upper edge of the plate 35 is disposedrearward of the natural path of gravitation of the ore and issufficiently spaced from the outer face of the plate 25 to permitmagnetic particles separated from the ore to drop downward between saidplates. The plate 35 narrows towards its lower end and forms a floor orbottom of the chute 33. Flange portions of the chute 33 are pivoted at36 to blocks 3'! which are slidably supported on rocker arms 38. Therocker arms 38 are pivoted intermediate their ends at 33 upon thebracket 28. Adjusting screws 40 are turned through screw threadedsleeves 4| carried on the outer ends of the arms 38 and are suitablyconnected with the blocks 31, so that when the screws are turned theblocks will be moved to carry the upper edge of the plate 35 toward orfrom the plate 25.

The arms 38 may be rocked on their pivots to raise and lower thedeflecting plates 35. Themeans for rocking or adjusting these armscomlocated above the liquid. A movable contact member I normally standsin engagement with the block 660. This maintains the electromagnetscontrolled by the device in a fully operative, normal condition. When itis desired to interrupt the supply of current, the contact I06 is swungaway from the block 880 and it is finally brought into engagement withthe block 640 to short-circuit the electromagnets. The contact I06 isfast upon a shaft I0'I, which shaft has fast upon it a pinion I08. Arack I09 meshes with the pinion I08 and isnormally drawn toward theleft-hand limit of its movement by a coil spring IIO which is secured tothe rack bar and to a fixed frame member III. The rack I09 forms aprolongation of the armature II2 of a solenoid 16a which is controlledin the same manner and for the same purpose as the solenoid 16 inFigure 1. When the solenoid 16a is energized, the contact I08 is swungaway from the contact 660 through nearly 360 into engagement with thecontact 640. When the electromagnet 16a is de-energized, the spring IIOreturns the contact I06 to its initial position.

The structure described can be used efficiently upon finely dividedmagnetic ore from any source. It has been found in practice to servevery advantageously for separating out the magnetic constituents ofcertain sea sand deposits which are rich in magnetic material. A singledeposit may include, for example, magnetite, martite, chromite, ilmeniteand rubies. All of these ore constituents are found in various degreesof purity in the original sand. No definite degree of magnetic densitiescan be specified, therefore, until the ores are tested, but it has beenfound that in any given deposit the several constituents are quiteuniform and bear a substantially uniform relation to one another.

In a specific ore body if the magnetic density found to be required forthe separation of magnetite may be taken as unity for the purpose ofcomparison with the densities of the magnets for separating the otherconstituents. The magnets of the first series, units 2 to would all bedesigned alike and would all have this same density of 1.

Martite would then require for its separation magnets having a densityof 1.7 to 2; chromite 3.57 to 4.3; ilmenite 5.7 to 6.43; and rubies orgarnets up to 8.57. The magnets of the second series, that is 6 to 9,would be designed alike to have densities between 1.7 and. 2; those of athird series to have densities between 3.57 and 4.3; those of a fourthseries to have densities be tween 5.7 and 6.43; and those of a finalseries to have densities up to 8.57. The above figures are of course tobe regarded merely as illustrative since it is possible to vary thenumber of stages or series and to design the magnets in accordance withthe conditions found necessary by analysis of the ore body.

I claim:

1. In an ore separator, in combination, an electromagnet, a source ofcurrent, a circuit including the electromagnet and said source forsupplying current from the source to the electromagnet, intermittentlyacting 'means for gradually increasing the resistance of said circuit,and means for shunting the source around the electromagnet and forshort-circuiting theelectromagnet when the maximum resistance isreached, comprising a body of conductive liquid, a first stationarycontact submerged therein, a second stationary contact located at asubstantial distance from the first, lower and upper movable contacts,the lower contacts being submerged and normally in engagement with thefirst stationary contact and the upper movable contact being locatedabove the level of the liquid, and means for moving the movable contactsto separate the lower one from the first stationary contact and to carrythe upper one into engagement with the second stationary contact.

2. In a magnetic ore separator, in combination, a succession ofelectromagnets of progressively increasing magnetic densities withassociated current supply circuits, means for delivering oresuccessively past said electromagnets to separate and classify the oreconstituents according to the magnetic characteristics thereof, andmeans for intermittently effecting a momentary reduction of theintensities of certain of the electromagnets to overcome adhesion of theore, comprising means for first causing the resistance between theelectromagnets and the source of current to be increased smoothly andthen shunting the source current around the electromagnets.

3. In a magnetic ore separator, in combination, a succession ofelectromagnets of progressively increasing magnetic densities withassociated current supply circuits, means for delivering oresuccessively past said electromagnets to separate and classify the oreconstituents according to the magnetic characteristics thereof, andmeans for intermittently effecting a momentary reduction of theintensities of certain of the electromagnets to overcome adhesion of theore, comprising means for first causing the resistances between theelectromagnets and the source of current to be rapidly and smoothlyincreased and for then short-oircuiting the electromagnets.

4. A magnetic ore separator comprising a frame, a plurality of magnetsarranged one above the other in the frame, a support for each magnetpivotally mounted on the frame, an adjusting screw for each supportmounted on the frame and bearing at one end against the support in suchmanner as to hold'the support and magnet in adjusted position, saidscrew being disposed at the front of the separator, a rocker arm pivotedon each support, a metal plate carried by each support and extending infront of the magnets and above the support, a hopper supported on theupper end of each plate, one end of said rocker arm extending outwardlyin front of the metal plate, a deflecting plate laterally adjustablysupported upon the last named end of said'rocker arm, means at the frontof the metal plate for adjusting the deflecting plate, and means at thefront of the metal plate for adjusting the rocker arm of each support.

5. A .magnetic ore separator comprising a frame, a plurality of magnetsarranged one above the other in the frame, a support for each magnetpivotally mounted on the frame, an adjusting screw for each supportmounted on the frame and bearing at one end against the support in suchmanner as to hold the support and magnet in adjusted position, saidscrew being disposed at the front of the separator, a rocker arm pivotedon each support, a metal plate carried by each support and extending infront of the magnets and above the support, a hopper supported on theupper end of each plate, one end of said rocker arm extending outwardlyin front of the metal plate, a deflecting plate laterally adjustablysupported upon the last named end of said rocker arm, means at the frontof the metal plate for adjusting the deflecting plate, means at thefront of the metal plate for adjusting the rocker arm of each support,and means at the front of the separator for adjusting said hopperrelative to said plate.

6. In a magnetic ore separator, an electromagnet unit comprising poleplates, a winding on one of the pole plates, said pole plate havingcommunicating grooves in the faces thereof forming a continuous channel,cover plates covering and closing the open sides of thegrooves to formtherewith a continuous passage, and means for delivering cooling fluidto one end of the passage and for discharging it from the other end ofthe passage.

'7. In a magnetic separator, an electromagnet unit comprising a poleplate, a stem thereoma winding on the stem, a smooth face plate ofnonmagnetic material on the pole plate, means for continuously effectinga free gravity feed of ore particles past the face plate, and a pole barin front of the face plate at the opposite side of the ore path from theface plate adjacent the upper end of the face plate to concentrate thelines of magnetic force in the region where the ore velocity is low, andmeans for discharging the diverted, magnetic ore separately from theresidue, the pole plate under the face plate being horizontally serratedto cause the magnetic flux to be distributed over the face of the plate.

DONALD M. CRIST.

prise screws 42 mounted in bearings 43 and 44, the bearings 43 beingscrew threaded. Ends of the screws 42 engage ends of the arms 38 in suchmanner that when the screws are turned in one direction the forward endsof the arms will be lifted, whereas on reverse movement of the screwsthe forward ends will be lowered. As the forward ends of the arms 38 areraised, the deflecting plate 35 will be moved upward and closer to theplate 25. The provision for bodily adjusting the plate 35 throughadjustment of the screws 40 permits the setting of the plate 35 at thedesired angle and position relative to the plate and the other elementsof the units. These adjustments are made to adapt the apparatus to thecharacteristics of the particular ore being treated and to the characterof the separation desired. The hoppers 22 may be adjusted by means ofadjusting screws 45. The screws 45 are mounted on the lower ends of thehoppers and are adapted to bear upon the plate 25 just where the platecurves around the upper end of the bracket 28. By means of thisadjustment, the spacing of the discharge spout of the hopper from theplate 25 may be varied as desired.

To provide for adjusting the entire unit, the bracket 28 is swung on.its pivot 29. This is accomplished by means of adjustingscrews 46mounted in brackets 41 fastened on the frame 30. Ends of these screwsbear against the forward l wer portions of the brackets 28. By turningthe screws in one direction, the bracket 28 is caused to be pushedupward and rearward and the hoppers 22 and the deflecting plate 35, bothwith their associated elements, are likewise moved. Reverse adjustmentsmay obviously be made by turning the screws 46 in the oppositedirection.

These adjustments vary the inclination of the electromagnet 25 andprovide for moving the electromagnet toward and away from the path ofgravitation of the ore.

The adjustments can be quickly and easily made to adapt the elements ofthe several units for various kinds of separating operations, dependingupon the class of Work to be done and the characteristics of the ore tobe treated. These adjustments further permit an arrangement of theelements of the units such that there will be no appreciable waste orloss and hence a greater yield of the desired ore constituents. The poleplates or cores for the electromagnets of the second and third seriesare provided with water passages 26a. and 27a in order that these platesmay be water-cooled. Leading to these passages from a suitable source ofwater supply (not shown) are pipes 260 and 26d, and 210 and 21d, forcausing the circulation .of the water through the passages of the poleplates.

The pole plates 26 have grooves formed in the inner faces thereof andthe inner faces are covered by plates 26a. The water enters through apipe 260 and leaves through a pipe 26d. The arrangement of the passages21a is illustrated in Figure 8. The water enters through a pipe 210 andleaves through a pipe 21d. Cover plates 2'Ie are applied to the upperand lower faces of the pole piece 21 to close the open sides of channelsformed in the upper and lower faces of the pole piece so as to providethe continuous communicating passages 21a as illustrated.

This cooling of the pole plates and cores is desirable since the finelydivided ore is usually quite hot when passing through the working zonesof the magnetic separator, it being desirable to pass the ore through adrier before subjecting it to the action of the separator. The heatgenerated in the high density electromagnetic equipment together withthe heat from the ore is apt to interfere with successful operation andto damage the magnets, and for this reason the water cooling of thepoles is desirable.

A In the units of the later series there is a tendency for the separatedore particles to adhere to and collect upon the faces of the plates 25and it becomes necessary from time to time to release or remove theaccumulation in order to prevent defective operation.

Current is supplied to all of the electromagnets from a suitable sourceof current such as a generator 48. One terminal of the generator isconnected through a conductor 49 with a terminal 50. The terminal 50 isconnected through a conductor 5| with a terminal 52 which in turn isconnected with a trunk line 53 from which branch lines 54 run to thewindings of the electromagnets of the last series. The current flowingthrough these electromagnets passes through branch lines 55 to a trunkline 58 which is connected to a terminal 51 of a circuit breakingmechanism. The terminal 51 is connected through a movable conductor 58with a terminal 59 which in turn is connected through conductors 68, SIand 62 to the opposite side of the generator. Through the circuitdescribed, the electromagnets of the last series are normally fullyenergized, but when it is desired to release the accumulating ore on thefaces of. the plates 25 of the units l4, l5, l6 and I1, provision ismade first to interpose an increasing resistance in the circuits ofthese units and then to short-circuit the electromagnets and shunt thegenerator around the electromagnets. To this end, the terminal 52 isconnected through a conductorBS with a contact 64, and the conductor 58is moved to cause an increasing resistance to be interposed between theterminals 51 and 59.

The details of this mechanism are best illustrated in Figures 1 and 4.The conductive rod 58 carries at the lower end thereof a convex metalliccontact block 58a which is constantly immersed in a conductive solution65. Normally, the convex contact block 58a is in direct engagement witha concave contact block 66 mounted in the bottom of the vessel 61 whichcontains the conductive liquid 65. From time to time, however, anddesirably at intervals of several seconds, the conductive rod 58 ismoved upward to break the direct contact of the blocks 64 and 66 and tocause the resistance between them to be gradually increased. The rod 58has fast upon it a conductive block 68 upon which the terminal 51 iscarried. The block 68 has a slot in one the resistance between theblocks 58a and 66 without completely cutting off the current supply fromthe electromagnets. Finally, however, a contact 11 carried by the block68 is moved into engagement with the contact 64 to short-circuit theelectromagnets of the last series. At this time the block 58a is stillsubmerged in liquid so that the generator circuit is not interrupted butincludes a high resistance because of the wide separation of the blocks58a and 66. In the initial separation of the blocks 58a and 66 auxiliarycontacts 18 and I9 carried by them are maintained in engagement so as toavoid too sudden an increase of the resistance. The contact I8 iscarried by a plunger 89 mounted in a bore of the block 64 and theplunger is urged toward the lower limit of its movement by a leaf spring8i.

The contact TI is carried by a plunger 82 which is mounted in a bore ofthe block 68 and is urged to the upper limit of its movement by a coilspring 89.

The blocks 58a and 66 are made convex and concave, respectively, inorder that the trapped liquid may serve to cushion the relative approachof the blocks and thus prevent violent re-engagement of them when thesolenoid I6is de-energized. In order to prevent the liquid frominterfering, however, with the complete re-engagement of the blocks,provision is made of a small bore 84 through which the liquid may escapefrom the cavity of the block 66.

The solenoid I6 is connected through a conductor 85 with the terminal52. The opposite end of the winding ofv the solenoid I6 is connectedthrough a conductor 86 with a stationary contact 86a. A disc 81 isdriven through a pulley 88 and a belt 89 from a motor 90. The disccarries a contact which wipes across the stationary contact 81periodically. The stationary contact 9! is in continuous conductiverelation with the disc and the disc carried contact. The contact 9I isconnected through a conductor 92 and conductor 62 to the generator.During the brief period of engagement of the disc contact with thestationary contact 81, the solenoid I6 is energized, the rod 58 is drawnupward quickly, the resistance of the generator circuit is increased andthe ore separating magnets are short-circuited. As soon as the disccontact leaves engagement with the contact 9|, the solenoid I6 isde-energized and the rod 58 together with the blocks 58a and 69 returnsdownward to the normal position. This entire cycle of movement requiresonly a small fraction of one second.

The electromagnets of the units I0, II, I2 and I3 are similarlycontrolled and so also are the electromagnets of the units 6, I, 8 and9. Since the circuits of these electromagnets are in no way differentfrom the electromagnet circuits already described, they will not bedescribed in detail. Corresponding parts have been numbered with thesame numbers but with the subscript a added in the case of units I9, II,I2 and I3, and with the subscript b added in the case of units 6, I, 8and 9.

The electromagnets of the last series of units are mounted upon theframe in the same way as the electromagnets of the other units and areprovided with similar means of adjustment. The electromagnets of thelast series of units It, I5, I6 and H are however desirably constructedin a somewhat difierent manner from the electromagnets of the precedingseries. Such construction is illustrated in Figures 9 and 10 in thisform. Each electromagnetic unit comprises a pole plate 92 whose faceadjacent the plate 25 is serrated or notched in order to cause the linesof magnetic force to be distributed throughout the height of the plate.The plate 92 has a stem 93 on which a winding 94 is mounted. A U- shapedmember 93a is bolted to the rear end of the stem 93 and has forwardlyreaching arms 93b disposed outside the frame members. Further arms 930are pivotally mounted upon the arms 93b by means of pivotbolts 93d. Thearms 930 are provided with arcuate slots 93c concentric with the pivotbolts 93d. Threaded studs 93 carried by the arms 93c extend throughthese slots and. receive upon their outer ends lock nuts 93g for fixingthe arms 930 in selected adjusted positions. At their forward ends thearms 930 are twisted so that they are disposed fiatwise and these flatportions are provided with slots 93h, which extend toward and from thepole plate 92. A pole bar 95 is adjustably mounted upon the arms 93c bymeans of bolts 91 and lock nuts 96. It will be observed that pivotaladjustment of the arms 93c is eifective to raise or lower the pole bar95 and the bodily adjustment is effective to move the pole plate to andfrom the path of falling ore. The pole plate 92 may be regarded as thepositive pole and the bar 95 as the negative pole. The pole bar 95 actsto converge and concentrate the linesof force in front of the upper partof the plate 25 so that the ore particles are acted upon with greatmagnetic force while travelling at low velocity. It is important,however, that the pole bar 95 be adjusted to lie farther from the pathof the falling ore than the directly opposed portion of the pole plate92, since the pole bar 95 also tends to draw the magnetic ore particlestoitself.

It will be noted that the pole plate 92 is in this instance extendedupward into engagement with the sloping face 3| of the plate 25, so thatthe ore is subjected to the magnetic influence while actually in contactwith the face 3|. At this point the only particles remaining in thegauge which may be desirable are very slightly influenced owing to theirlow susceptibility by magnets of extreme magnetic density and it isfound advisable to slow their gravitation as much as possible. This isfeasible in the last stage since the ore particles which are to berejected are non-magnetic and cannot, therefore, become attached tomagnetized particles even when in contact with them.

The bar 95 is carried upon arms 96 being securedthereto by means ofbolts 91 and nuts 98, the bolts being passed through slot 99 in the arms96 so that the bar 95 can be adjusted at will toward and from the plate25. The arms 96 are pivotally mounted at 91 and are adapted to be fixedin position by means of wing nuts I00 which are threaded upon stems I0]carried by the machine frame. The stems IflI pass through arcuate slotsI92 formed in the arms 96 concentric withthe pivots 9'1.

In Figures 11 and 12 disclosure is made of a modified form ofinterrupter mechanism. This mechanism is designed to be used in lieu ofthe solenoid operated mechanism of Figures 1 and 4. It has the advantagethat the contacts to be separated for interposing an increasingresistance in the circuits of the ore separating magnets may beseparated to a greater extent than would be feasible in the case of theblocks 58a and 66. This separator mechanism comprises an annular dish orvessel I03 of suitable nonconducting material, such as porcelain,"whichcontains a conductive liquid I04. or channel of this vessel has apartition I95 provided in it with a contact block 660 at one side of thepartition submerged in the liquid and a contact block 640 at the otherside of the dam 70 The trough

